Maximum slope of drain line?

The minimum slope for a pvc plumbing drain line is 1/4" per foot (some jurisdictions wil allow 1/8th"). What is the maximum slope allowed? :slight_smile:

You can go straight up. Can you explain the question.

I remember there was an ideal slope. Anything other than that was bad. Too low, nothing drains. Too much, the liquid leaves behind the solids.


Good question, all I could find was this:

**Slope. **The horizontal combination waste and vent pipe shall have a maximum slope of one-half unit vertical in 12 units horizontal (4-percent slope).

The “no” zone is anything between: 1/2" per foot and a 45 degree angle. 45 degrees to vertical is considered vertical and is okeedoekee.

Thanks Charles - that’s what I was looking for. :slight_smile: I found a drain line right at 1/2" per foot. Where did you find that reference?

I also know the max to be 1/2" per foot (until you get to 45 degree or more) but I don’t have a referance